1. Technical Field
The present invention relates generally to a direction control assembly for an aerospace vehicle and, more particularly, to a flap assembly at the forebody of a reusable launch vehicle for rotating and stabilizing the vehicle during entry and pre-landing maneuvers.
2. Discussion
Reusable launch vehicles used to deploy satellites in a predetermined orbit about the earth include single stage to orbit ("SSTO") vehicles that are designed to perform their intended operation and return to earth without jettisoning any portions of the vehicle. Accordingly, SSTO vehicles do not include discardable booster rockets or fuel tanks. Rather, the fuel supply elements of SSTO vehicles are retained throughout the flight thereby increasing the need to minimize fuel consumption in order to decrease the unusable weight carried into orbit. The present invention addresses these concerns by providing a vehicle rotation and control mechanism that reduces propellant acquisition subsystems and the propellant required to properly position the vehicle for landing.
Vertically landing SSTO vehicles commonly include a conically shaped airframe configured for stable flight in a nose-forward orientation. However, since the vehicle is vertically landed in a rearward or tail-first orientation a rotation of the vehicle during the landing sequence is required. Currently, SSTO vehicles of this class perform the rotation maneuver through the use of engine power. More specifically, the maneuver includes starting several of the main engines, retracting entry flaps so that the vehicle pitches up to initiate rotation, and selectively throttling up the engines to arrest rotation and place the vehicle into the desired base-first orientation. In order to minimize the quantity of propellant consumed by the engines between the rotation and touch down phases of the landing procedure, this rotation maneuver is generally conducted at a relatively low altitude. While this procedure is viable, a considerable amount of propellant is used during the starting and operation of the engines and the propellant feed system becomes heavy and complex. Further, the relatively low altitude compresses landing functions into a shorter timeline.